Fuel injectors are already known which are for example equipped with a piezoelectric actuator. The piezoelectric actuator has the characteristic that on the one hand it can convert an electric signal very quickly into a mechanical lifting movement. In addition, the piezoelectric actuator has the characteristic that, in the event of a mechanical compressive load, it emits an electric signal so that it at the same time can be used as a sensor for recording the prevailing pressure in the fuel injector or in the injection system.
Assisted by the mechanical lifting movement of the actuator, a nozzle needle is controlled by means of which injection holes within a nozzle unit can be opened wide or less wide. By recording the current pressure or the dynamic change in the fuel injector, it is possible to decide on the lifting movement of the nozzle needle. In this way, the nozzle needle can in the case of a corresponding forming of an electric control signal be controlled to a specific, predetermined position.
However, known electronic management systems for controlling combustion engines are not in the position to achieve a low-emission and low-consumption operation of the internal combustion engine to a sufficient extent with the assistance of a position-controlled fuel injector.
In addition, it is also known that the mixture-forming process within a cylinder of the internal combustion engine can essentially be influenced by the exchange of gas as well as the fuel injection volume and by the course of the injection rate. Until now, this problem was solved by the fuel injector used, because of constructional measures, having corresponding hydraulic-mechanical features. However, these measures do not suffice to meet all the requirements for future combustion requirements, in particular also with respect to planned legal regulations.
A further problem also consists in that the exact recording of the actually injected fuel quantity as well as the point in time of the injection has only been able to be resolved unsatisfactorily thus far. In particular, problems arise because the fuel injectors used are manufactured with an inevitable manufacturing tolerance, so that the problem of accurately recording of the fuel quantity actually injected has thus far only been resolved in an unsatisfactory manner.